1. Field of the Invention
The present invention relates to a dry clutch facing, e.g., a clutch facing for a dry friction clutch used in a vehicle such as an automobile, and a process for producing such clutch facing.
2. Description of the Related Art
A clutch facing of the mentioned type is conventionally produced through a spirally winding step of winding into a volute shape a continuous fiber material including a rubber, an uncured thermosetting resin, a friction improving agent and the like, e.g., a roving. This clutch facing may be used in a clutch disk of a separate cushion type in which for example, a plurality of cushion springs are riveted to a disk plate in order to smoothen the engagement of the clutch.
In the clutch facing made through the spirally winding step as described above, however, a peculiar distortion may be generated after the production of the clutch facing in some cases. In such a case, a curing operation must be carried out, resulting in an inevitable increase in manufacture cost. When a clutch disk as described above is used severely, each clutch facing may be worn at its back due to the friction contact with the cushion springs.
Accordingly, it is an object of the present invention to provide a dry clutch facing of the above-described type, wherein the distortion and the wearing of the back can be inhibited considerably.
To achieve the above object, according to the present invention, there is provided a dry clutch facing, comprising a facing element which is comprised of a continuous fiber material which is wound into a volute shape and impregnated with a rubber, a thermosetting resin and a friction improving agent, and a reinforcing element which includes a matrix formed of a thermosetting resin, and a reinforcing short fiber dispersed uniformly and at random in the matrix, the reinforcing element being bonded to a back of the facing element and placed in contact with a cushion spring.
With the above arrangement, the reinforcing element hardly generates distortion. Therefore, even if a distortion is generated in the facing element, such distortion is inhibited remarkably due to a backing effect provided by the reinforcing element. In a separate cushion-type disk, the cushion spring is placed in contact with the reinforcing element of each clutch facing. Therefore, even if a friction contact is produced between the cushion spring and each clutch facing under severe service conditions, the wearing of each clutch facing is inhibited considerably. This also applies to a plate cushion-type clutch disk in which a disk plate itself also serves as a cushion spring.
The reinforcing element bears the strength of the dry clutch facing. Therefore, it is possible to moderate the strength condition in the facing element and to widen the range of regulation of the friction characteristic. Thus, the dry clutch facing has a friction characteristic suited to detailed market needs.
It is another object of the present invention to provide a producing process of the above-described type, which is capable of mass-producing a dry clutch facing of the above-described type.
To achieve the above other object, according to the present invention, there is provided a process for producing a dry clutch facing, comprising the steps of:
forming an annular preform for a facing element through a step of winding a continuous fiber material including a rubber, an uncured thermosetting resin and a friction improving agent into a volute shape;
forming an annular preform for a reinforcing element through a step of heating, under a pressure, an annular accumulated material which includes a reinforcing short fiber and a resin powder of an uncured thermosetting resin, the reinforcing short fiber being dispersed uniformly and at random in the entire resin powder; and
superposing both the annular preforms one on another and heating the annular preforms under a pressure, thereby producing a facing element and a reinforcing element and at the same time, bonding both the facing and reinforcing elements to each other.
When such process is employed, a dry clutch facing having an arrangement as described above can be produced efficiently on a mass-production scale.
The above and other objects, features and advantages of the invent ion will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.